This invention relates to a powder feed apparatus and a powder feed apparatus control method for feeding powder into a powder molding press for molding powder.
Various powder feed apparatuses for feeding powder into a die on a die plate when press-molding a compact of a predetermined shape using a powder molding press have been proposed. As these powder feed apparatuses, hose types, shutter types and rotary types and the like have been proposed. For example, a shutter type powder feed apparatus is one wherein a fixed quantity of powder from powder stored in a hopper is fed into a die by a shutter being opened and closed, and a rotary type powder feed apparatus is one wherein powder in a hopper is fed in a fixed quantity into a die by a rotary shutter interposed between the hopper and a feeder being rotated.
FIG. 12 is a sectional side view of a main part of a conventional hose type powder feed apparatus. This overall powder feed apparatus 1 feeds a fixed quantity of a powder 3 stored in a hopper 2 through a hose 4 into a feeder 8 disposed on the upper side of a die 7 mounted on a die plate 6 of a powder molding press 5.
With the feeder 8 moved in the direction E together with the hose 4, by cooperative movement of an upper punch 9 and a lower punch 10 of the powder molding press 5, powder 3 inserted into the die 7 is compressed to form a compact. By the feeder 8 being moved over the die plate 6 in the direction E, the powder in the feeder 8 is scraped into the die 7 so that a predetermined quantity of powder 3 remains in the die 7 only.
As a driving device for sliding this feeder 8 in the arrow D-E direction, the kind of cam type driving device shown in FIG. 13 has been widely used. FIG. 13 is a view showing part of a feeder driving mechanism 11 and illustrating the operation thereof, wherein a rotational force of a motor or the like is applied to the end of a first feeder lever 12, the first feeder lever 12 converts this rotational force into an oscillating direction force and about a support point 13 as center forms a pushing force by means of a biasing force of a spring 17 toward a pin 15 provided on the end of a second lever 14. The pin 15 is abutted with the cam 16 and the cam 16 is rotated for example clockwise as shown by the arrow F. The feeder 8 is linked to a cam shaft 18 and the feeder 8 is caused to slide along the die plate 6 in the arrow D-E (see FIG. 12) direction.
The cam surface of the cam 16 is formed to predetermine the sliding direction of the feeder 8 over the die 7 and the speed thereof and so on in accordance with the powder feed quantity and the material of the powder 3 and the like.
However, with the construction of the powder feed apparatus described above, there has been the problem that because it is necessary to form the cam surface of the cam 16 in advance so as to describe the movement curve of the feeder with a feeder cam, it has been necessary to exchange the cam 16 every time the shape of the compact being molded changes.
In recent years, powder-molding work lots have become smaller and more diverse, shapes of compacts also have from simple ones become complicated and large and furthermore there is a demand for moldings of special materials.
Affects of the quality of the powder during this kind of powder molding pressing, on nonuniformity of density of powder in the die, dispersion per unit weight and the accuracy of the thickness (and parallelism) of the compact and so on, constitute a problem, and to avoid the trouble of exchanging the cam every time the shape or material of the molded compact changes it has been made possible to combine insert cams with a cam serving as a base and make slight pattern changes using insert cams. That is, setting of the positions of the feeder 8 in its sliding direction on the die plate 6 has been carried out by positional adjustment of links, levers and insert cams and the like, but this adjustment work requires skill and its reproducibility is not good and this has been a cause of dispersion in compact products.